1. Field of the Invention
The present invention relates to a small size air pump which aspirates air from within a space occupied by a rotary member disposed in an instrument, thereby preventing air resistance in the rotary member, heat in the occupied space, and the like from occurring.
2. Related Background Art
An example of air pump structure is disclosed in WO 94/20755, U.S. Pat. No. 5.639.226. The air pump disclosed in this publication has a configuration for use in bicycles, in which the pump is actuated by a portable battery, such that a driving gear disposed at the output shaft of the motor and a crown gear mesh with each other, whereas the rear end of a piston rod is axially supported by the crown gear so as to axially support a cylinder itself in a swinging fashion. Due to such a configuration, the torque of motor is transmitted to the piston rod by way of a speed-reducing mechanism, so as to actuate the cylinder/piston pump.
The above-mentioned conventional air pump has a problem as follows. The speed-reducing mechanism based on a combination of the driving gear and crown gear, which is employed for compensating for output characteristics of the motor, is considered to be effective when there is sufficient room in the space for installing the air pump as in the case of a bicycle. However, the above-mentioned air pump has been problematic in that it is hard to utilize in a state where the apparatus incorporating the air pump is so small that the space for installing and accommodating the air space is quite limited.
In order to overcome the above-mentioned problem, it is an object of the present invention to provide a small size air pump which has a simple structure and is less likely to incur restrictions on its space for installation and accommodation.
The present invention provides a small size air pump in which a motor is driven to actuate a pump section, so as to carry out a predetermined aspirating operation; the air pump comprising a worm gear disposed at an output shaft of the motor; a worm wheel, disposed between the motor and the pump section, meshing with the worm gear; a smaller gear disposed coaxial with the worm wheel; a larger gear, disposed at a position held between the motor and the pump section, meshing with the smaller gear; and an actuator element having one end pivotally connected to a periphery of a flat part of the larger gear and the other end connected to an end part of a piston of the pump section.
In this small size air pump, the output of motor can reliably be transmitted to the worm wheel due to a cooperating action between the worm gear disposed at the output shaft and the worm wheel. Also, a combination of smaller and larger gears rotating in synchronization with the worm wheel can easily set the reduction ratio. Employing such a gear train in an air pump can easily deal with the space for installing and accommodating the air pump even when the space is quite limited. When a small size motor with a small rotational torque is utilized, a slight power transmission loss may greatly affect characteristics of the air pump, which makes it important to employ an appropriate power transmitting mechanism. In this sense, the above-mentioned gear train can be considered optimal.
Preferably, the small size air pump further comprises a support plate connecting the motor and the pump section to each other; a first axle part of the worm wheel and smaller gear and a second axle part of the larger gear being arranged in the support plate; the motor, the pump section, and the larger gear being disposed in series in an axial direction of the output shaft. When such a configuration is employed, the larger gear is appropriately disposed between the motor and the pump section, whereby the air pump can be made smaller.
Preferably, the motor, the pump section, and a speed-reducing mechanism disposed between the motor and the pump section occupy a volume of 5 cm3 or less. Even under such a restriction of occupied volume, an air pump having a high compression ratio can be embodied.
Preferably, in the small size air pump, the motor has a barrel part having a volume of 5 cm3 or less. Such a motor can be considered to be a small size motor which hardly takes up a space for accommodating it.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.